Conventionally, various piezoelectric sensors which each detect a press on an operation surface and various touch panels which each include a piezoelectric sensor have been devised. For example, Patent Literature 1 discloses a touch panel which can simultaneously receive inputs of position information on a top surface of the touch panel and press information.
This touch panel includes a piezoelectric film and a detecting unit. The piezoelectric film is uniaxially stretched, and molecules are oriented in a uniaxial stretching direction. The piezoelectric film includes a first principal surface on which electrodes and connection wires are formed, and a second principal surface which opposes the first principal surface. The electrodes formed on the first principal surface of the piezoelectric film are connected to the detecting unit via the connection wires.
According to this configuration, the detecting unit detects a voltage produced in each electrode when a force is applied to a top surface of the touch panel. Thus, the detecting unit detects that the top surface of the touch panel has been pressed.
PTL 1: International Publication No. 2010/143528